Light-emitting device

ABSTRACT

Provided is a light-emitting device including a light-emitting element having a peak emission wavelength in a range of from 400 nm to 470 nm, and a fluorescent member including a first fluorescent material including an aluminate that contains Mg, Mn, and at least one alkali earth metal selected from the group consisting of Ba, Sr, and Ca, a second fluorescent material having a different composition from the first fluorescent material, and a third fluorescent material. The first, second and third fluorescent materials have a peak emission wavelength in a range of from 510 nm to 525 nm, from 510 nm to 550 nm, and from 620 nm to 670 nm, respectively. The light-emitting device has an emission spectrum with a relative emission intensity of 35% or less at 500 nm and of 65% or less at 540 nm when a local maximum light-emitting emission intensity in a range of from 510 nm to 535 nm is taken as 100%.

CROSS-REFERENCE TO RELATED APPLICATIONS

This application claims priority to Japanese Patent Application No.2017-004424, filed on Jan. 13, 2017, the disclosure of which is herebyincorporated by reference in its entirety.

BACKGROUND Technical Field

This disclosure relates to a light-emitting device.

Description of the Related Art

A light-emitting device known in the art may include a bluelight-emitting diode (LED) in combination with a green light-emittingfluorescent material and a red light-emitting fluorescent materialexcited by the blue light to emit white-based mixed light. Alight-emitting device included in an image display device, such as aliquid crystal display, is required to have a high luminous flux andreproduce colors in a wide range of chromaticity coordinates. Theevaluation standard for color reproducibility is, for example, NationalTelevision System Committee (NTSC) ratio standardized by NTSC.

For example, Japanese Patent Application Publication No. 2008-303331describes a light-emitting device for use in a liquid crystal displaythat is required to have a color reproducibility of 95% or more in NTSCratio. The light-emitting device includes a light-emitting elementhaving a peak emission wavelength in a range of from 390 nm to 550 nm, agreen light-emitting β sialon fluorescent material, and a redlight-emitting fluorescent material represented, for example, byCaAlSiN₃:Eu.

SUMMARY

A light-emitting device includes a light-emitting element and afluorescent member. The light-emitting element has a peak emissionwavelength in a range of from 400 nm to 470 nm. The fluorescent memberincludes a first fluorescent material, a second fluorescent material,and a third fluorescent material. The first fluorescent materialincludes an aluminate containing Mg, Mn, and at least one alkali earthmetal selected from the group consisting of Ba, Sr, and Ca, and has apeak emission wavelength in a range of from 510 nm to 525 nm. The secondfluorescent material has a different composition from the firstfluorescent material, and a peak emission wavelength in a range of from510 nm to 550 nm. The third fluorescent material has a peak emissionwavelength in a range of from 620 nm to 670 nm. The light-emittingdevice has an emission spectrum where the relative emission intensity at500 nm is 35% or less and the relative emission intensity at 540 nm is65% or less when the local maximum light-emission intensity in a rangeof from 510 nm to 535 nm is taken as 100%.

BRIEF DESCRIPTION OF DRAWINGS

FIG. 1 is a schematic cross-sectional view of an exemplarylight-emitting device according to the present disclosure.

FIG. 2 is a schematic cross-sectional view of another exemplarylight-emitting device according to the present disclosure.

FIG. 3 shows emission spectra of fluorescent materials included in thelight-emitting devices according to examples of the present disclosureand comparative examples.

FIG. 4 shows emission spectra of light-emitting devices according toExamples 1 to 4 of the present disclosure and Comparative Examples 1 to3.

FIG. 5 shows emission spectra of light-emitting devices according toExamples 5 and 6 of the present disclosure and Comparative Examples 1and 4 to 6.

FIG. 6 shows emission spectra of light-emitting devices according toExample 7 of the present disclosure and Comparative Examples 1 and 7 to9.

FIG. 7 shows emission spectra of light-emitting devices according toExamples 8 to 10 of the present disclosure and Comparative Examples 10and 11.

DETAILED DESCRIPTION

A liquid crystal display includes color filters each for transmittingred light, green light, or blue light. The filters transmit a part oflight emitted from a light-emitting device and combine three primarycolors of light: red, green, and blue to represent color. Thus, alight-emitting device having an emission peak with a narrow halfbandwidth in each of the wavelength regions of red, green, and blue inthe emission spectrum has high color purity in each wavelength region,resulting in improved color reproducibility.

The β sialon fluorescent material described in JPA No. 2008-303331 has arelatively wide half bandwidth of the emission spectrum, and a peakemission wavelength at a relatively long wavelength. With regard tovisibility, the β sialon fluorescent material has a part of its emissionspectrum in the wavelength range that contributes to improvingluminance, and has relatively more light-emitting components in thatwavelength range than other fluorescent materials known in the art.Thus, the β sialon fluorescent material of Patent Literature 1 is moreluminous than other fluorescent materials known in the art. However, asthe emission spectrum has a relatively wide half bandwidth, the β sialonfluorescent material of Patent Literature 1 has a low green colorpurity. This can limit further expansion of the color reproduction rangeof a liquid crystal display including the light-emitting device. Thus,there is a need for an improved light-emitting device including a βsialon fluorescent material and having higher luminance and a widercolor reproduction range for use as a light source for a high-definitionliquid crystal display.

One or more embodiments of the present disclosure are directed to alight-emitting device that can achieve both high color reproducibilityand high luminance when used in a liquid crystal display.

A specific means for solving the issue is as described below, andincludes the constituent elements described below. One aspect of thepresent disclosure is a light-emitting device including a light-emittingelement and a fluorescent member. The light-emitting element has a peakemission wavelength in a range of from 400 nm to 470 nm. The fluorescentmember includes a first fluorescent material, a second fluorescentmaterial, and a third fluorescent material. The first fluorescentmaterial contains an aluminate containing at least one alkali earthmetal selected from the group consisting of Ba, Sr, and Ca, as well asMg, and Mn, and has a peak emission wavelength in a range of from 510 nmto 525 nm. The second fluorescent material has a different compositionfrom the first fluorescent material, and a peak emission wavelength in arange of from 510 nm to 550 nm. The third fluorescent material has apeak emission wavelength in a range of from 620 nm to 670 nm. Thelight-emitting device has an emission spectrum where the relativeemission intensity at 500 nm is 35% or less and the relative emissionintensity at 540 nm is 65% or less when the local maximum light-emissionintensity in a range of from 510 nm to 535 nm is taken as 100%.

A light-emitting device according to an embodiment of the presentinvention will now be described. However, the embodiment described belowis a mere example for embodying the technical concept of the presentinvention, and the present invention is not limited to thelight-emitting device described below. The relationship between thecolor names and the chromaticity coordinates, the relationship betweenthe wavelength ranges of light and the color names of monochromaticlight, and others are in accordance with Japanese Industrial Standard(JIS) Z8110. For the amount of each component contained in acomposition, when a plurality of substances corresponding to thecomponent is present in the composition, the amount of the componentmeans the total amount of the substances present in the compositionunless otherwise specified.

Light-Emitting Device

A light-emitting device 100 according to the present embodiment includesa light-emitting element 10, and a fluorescent member 50. Thelight-emitting element 10 has a peak emission wavelength in a range offrom 400 nm to 470 nm. The fluorescent member 50 includes a firstfluorescent material 71, a second fluorescent material 72, and a thirdfluorescent material 73. The first fluorescent material 71 includes analuminate containing at least one alkali earth metal selected from thegroup consisting of Ba, Sr, and Ca, as well as Mg, and Mn, and has apeak emission wavelength in a range of from 510 nm to 525 nm. The secondfluorescent material 72 has a different composition from the firstfluorescent material 71 and a peak emission wavelength in a range offrom 510 nm to 550 nm. The third fluorescent material 73 has a peakemission wavelength in a range of from 620 nm to 670 nm. Thelight-emitting device 100 has an emission spectrum having a relativeemission intensity at 500 nm of 35% or less and a relative emissionintensity at 540 nm of 65% or less when the local maximum light-emissionintensity in a range of from 510 nm to 535 nm is taken as 100%.

The light-emitting device 100 includes the first fluorescent material71, which has a specific composition and an emission wavelength in arange of from 510 nm to 525 nm, in combination with the secondfluorescent material 72, which has a peak emission wavelength in a rangeof from 510 nm to 550 nm, as a green light-emitting component having alocal peak emission in a range of from 510 nm to 535 nm. Thiscomposition can reduce the amounts of the light-emitting components inthe blue-green region and the yellow-green region in the emissionspectrum to a certain amount or less, and can further increase theamount of the green component, which has superior color reproducibility.In other words, emissions of blue, green, and red in the respectivewavelength regions are emphasized in the emission spectrum of thelight-emitting device 100. Thus, a liquid crystal display including thelight-emitting device 100 can have a wider color reproduction range. Inparticular, a high-definition liquid crystal display including thelight-emitting device 100 can exhibit superior numerical valuesaccording to BT. 2020, which is a standard for a color reproductionrange, and can achieve a wider color reproduction range compared to thecase of using a light-emitting device known in the art.

The light-emitting device 100 can achieve both high colorreproducibility and high luminance of a liquid crystal display. Thereason for this may be as follows: The green wavelength region liesbetween the red and blue wavelength regions, and contains alight-emitting component that contributes to improving luminance inrelation to visibility. Thus, to produce a liquid crystal display havinghigh color reproducibility and high luminance, it is particularlyimportant to adjust the half bandwidth and the emission intensity of theemission spectrum in the green color wavelength region of thelight-emitting device to be used in a liquid crystal display. Alight-emitting device including the first fluorescent material having anemission spectrum with a narrow half bandwidth according to the presentembodiment can reduce the influence of green-light emission on red-lightemission and blue-light emission. This enables clear separation ofcolors of light through the color filters, resulting in an improvedcolor reproducibility of the liquid crystal display. Further, theemission spectrum of the second fluorescent material, which has a widehalf bandwidth, can increase the light-emitting component at around 555nm that contributes to improving luminance in relation to visibility inan extent not to affect the expansion of the color reproduction range.This enables a light-emitting device that can contribute to improvedcolor reproducibility and improved luminance of a liquid crystaldisplay.

The light-emitting device 100 will now be described in detail withreference to FIG. 1. The light-emitting device 100 is a surface mountlight-emitting device. The light-emitting device 100 includes thelight-emitting element 10, and the molded body 40, on which thelight-emitting element 10 is disposed. The light-emitting element 10 maybe a gallium nitride compound-semiconductor that emits visible light atshort-wavelengths (e.g., in a range of from 380 nm to 500 nm) and has apeak emission wavelength in a range of from 400 nm to 470 nm. The moldedbody 40 includes a first lead 20, a second lead 30, and a resin portion42 formed in an integral manner. The molded body 40 has a recess definedby a bottom surface and side surfaces, and the light-emitting element 10is disposed on the bottom surface of the recess. The light-emittingelement 10 has a pair of electrodes, positive and negative, and thepositive and negative electrodes are electrically connected to the firstlead 20 and the second lead 30, respectively, with a wire 60. Thelight-emitting element 10 is covered with the fluorescent member 50. Thefluorescent member 50 includes, for example, a resin and the fluorescentmaterial 70, which converts the wavelength of light from thelight-emitting element 10. The fluorescent material 70 includes thefirst fluorescent material 71, the second fluorescent material 72, andthe third fluorescent material 73.

The total fluorescent material 70 content in the fluorescent member 50relative to 100 parts by weight of the resin is, for example, 50 partsby weight or more, preferably 50.5 parts by weight or more, morepreferably 51 parts by weight or more, and still more preferably 60parts by weight or more, and also, for example, 300 parts by weight orless, preferably 250 parts by weight or less, more preferably 230 partsby weight or less, still more preferably 160 parts by weight or less.With the total fluorescent material content of the fluorescent member 50within the range above, light emitted by the light-emitting element 10can be efficiently wavelength-converted by the fluorescent material 70.

The fluorescent member 50 may further contain a filler, a light diffuseror other materials in addition to the resin which is a sealant and thefluorescent material 70. For example, a light diffuser when contained inthe fluorescent member 50 can ease directivity of light from thelight-emitting element 10 to increase the viewing angle. Examples of thefiller include silica, titanium oxide, zinc oxide, zirconium oxide, andalumina. When the fluorescent member 50 contains a filler, the fillercontent can be, for example, from 1 part by weight to 20 parts by weightrelative to 100 parts by weight of the resin.

The fluorescent member 50 serves not only as a wavelength conversionmember containing the fluorescent material 70 but also as a member forprotecting the light-emitting element 10 and the fluorescent material 70from outside environment. In FIG. 1, the first fluorescent material 71,the second fluorescent material 72, and the third fluorescent material73 are mixed and are present near the light-emitting element 10. Inother words, the fluorescent material 70 is arranged in the fluorescentmember 50 near the light-emitting element 10 rather than near the topsurface of the molded body 40. Arranging the fluorescent material 70near the light-emitting element 10 in this manner allows the wavelengthof light from the light-emitting element 10 to be efficiently convertedto produce a light-emitting device with high emission efficiency.However, the arrangement of the fluorescent material 70 in thefluorescent member 50 and the light-emitting element 10 is not limitedto one in which they are in close proximity to each other. Thefluorescent material 70 may be spaced apart from the light-emittingelement 10 in the fluorescent member 50 to reduce the influence of heatfrom the light-emitting element 10 on the fluorescent material 70. Theparticles of the fluorescent material 70 may also be approximatelyevenly dispersed throughout the fluorescent member 50 to emit light withfurther reduced color unevenness.

FIG. 2 is a schematic cross-sectional view of another example of thelight-emitting device 100 according to the present, disclosure. In FIG.2, the third fluorescent material 73 in the fluorescent member 50 isarranged near the light-emitting element 10, the second fluorescentmaterial 72 is arranged above the third fluorescent material 73, and thefirst fluorescent material 71 is arranged above the second fluorescentmaterial 72. This arrangement allows each fluorescent material to bemore efficiently excited by light emitted from the light-emittingelement 10.

Light-Emitting Element

The light-emitting element 10 emits visible light having an emissionspectrum at short wavelengths, e.g., in a range of from 380 nm to 485nm, and has a peak emission wavelength in a range of from 400 nm to 470nm, preferably from 430 nm to 470 nm, and more preferably from 440 nm to460 nm. The light-emitting element 10 having a peak emission wavelengthwithin the range above can increase the emission efficiency of the firstto third fluorescent materials.

As the light-emitting element 10, a semiconductor light-emitting elementincluding a gallium nitride semiconductor (In_(X)Al_(Y)Ga_(1-X-Y)N where0≤X, 0≤Y, and X+Y≤1) is preferably used. Using a semiconductorlight-emitting element as the excitation light source produces a highlyefficient light-emitting device that has high output linearity to theinput and is stable and resistant to mechanical impact. Thelight-emitting element 10 has an emission spectrum with a half bandwidthof, for example, 30 nm or less.

Fluorescent Member

The fluorescent member 50 contains the fluorescent material 70, and maycontain, for example, another fluorescent material, a resin, and a lightdiffuser as appropriate. The fluorescent material 70 contains at leastthe first fluorescent material 71 and the second fluorescent material72, which emit green light, and a third fluorescent material 73, whichemits red light.

First Fluorescent Material

The first fluorescent material 71 has a peak emission wavelength in arange of from 510 nm to 525 nm, and contains an aluminate containing Mg,Mn, and at least one alkali earth metal selected from the groupconsisting of Ba, Sr, and Ca. The alkali earth metal preferably containsat least Ba. When the aluminate contains Ba, the Ba content ratio in thealkali earth metal in the aluminate is, for example, 50 mol % or more,and preferably 70 mol % or more, and may be 99 mol % or less. The firstfluorescent material 71 may have a peak emission wavelength of from 510nm to less than 520 nm.

The first fluorescent material 71 preferably has a compositionessentially represented by formula (I) below. The fluorescent materialhaving a composition represented by formula (I) will hereinafter be alsoreferred to as “first fluorescent material (I)”.

X¹ _(p)Eu_(t)Mg_(q)Mn_(r)Al_(s)O_(p+t+q+r+1.5 s)  (I)

In the formula (I), X¹ is at least one selected from the groupconsisting of Ba, Sr, and Ca; and p, q, r, s and t satisfy 0.5≤p≤1,0≤q≤0.7, 0.2≤r≤0.7, 8.5≤s≤13, 0≤t≤0.5, 0.5≤p+t≤1.2, and 0.2≤q+r≤1.

In the first fluorescent material (I), X¹ preferably contains at leastBa. The first fluorescent material (I) containing Ba in its compositioncan maintain, for example, relatively high reflectance at its peakemission wavelength, and relatively low reflectance for light in theblue region. In other words, absorption of light in the blue region ishigh. This seemingly results in high emission intensity of the firstfluorescent material (I).

In formula (I), p is a total compositional molar ratio of X¹, which isat least one element selected from the group consisting of Ba, Sr, andCa. In the first fluorescent material represented by formula (I), if pis 0.5 or more and not more than 1, the first fluorescent material (I)may have an stable crystal structure, or may have a higher emissionintensity. p is preferably 0.6 or more, and more preferably 0.8 or more.p may also be 0.99 or less.

In formula (I), q is a compositional molar ratio of Mg. If q is 0.7 orless, the compositional molar ratio of Mg is low, and the relativeamount of Mn as an activating element is high. This may result in ahigher relative emission intensity. q is preferably 0.05 or more, andmore preferably 0.1 or more, and also preferably 0.65 or less, and morepreferably 0.6 or less. When q satisfies 0.0≤q≤0.7 in formula (I), thefluorescent material may have a peak emission wavelength in a range offrom 510 nm to 525 nm in the emission spectrum when excited by lightfrom the near-ultraviolet to blue region. The fluorescent material mayalso have a relatively low reflectance, and a greater emissionintensity. A liquid crystal display including a light-emitting devicecontaining the first fluorescent material 71 achieves high colorreproducibility.

In formula (I), r is a compositional molar ratio of Mn. Mn is anactivating element of the first fluorescent material (I). The firstfluorescent material 71 may further contain a rare-earth element, suchas Eu or Ce, as an activating element in addition to Mn. In particular,containing Mn and Eu as an activating element causes Eu to absorb lightto excite its electron. The excitation energy is transmitted from Eu toMn, and is expected to further contribute to the emission of Mn. Thiscan improve the emission intensity of the first fluorescent materialwhen excited by an excitation light source having a peak emissionwavelength in a range of from 400 nm to 470 nm. Thus, containing Mn andEu is preferable. In formula (I), if r is 0.2 or more and not more than0.7, for example, the reflectance may be low, and the emission intensitymay be high when excited by light in the near-ultraviolet to blueregion. In formula (I), if r is 0.2 or more, the activation amount of Mnis sufficient, the absorption of light is large, and the reflectance islow when excited by light in the near-ultraviolet to blue region. Thus,the first fluorescent material (I) may be able to have a high emissionintensity. In formula (I), if r is not more than 0.7, the activatingamount of Mn may be small, and concentration quenching may not occur inthe first fluorescent material (I), resulting in a higher emissionintensity. In formula (I), r is preferably 0.3 or more, and morepreferably 0.4 or more, and also preferably 0.6 or less, and morepreferably 0.55 or less.

In formula (I), q+r is from 0.2 to 1. If q+r is 0.2 or more and not morethan 1, the relative emission intensity may be sufficient. q+r ispreferably 0.3 or more, and more preferably 0.4 or more, and alsopreferably 0.99 or less, and more preferably 0.98 or less.

In formula (I), t is a compositional molar ratio of Eu. If t is not morethan 0.5, the emission intensity may be high. t is preferably 0.3 orless, and more preferably 0.2 or less.

In formula (I), p+t is from 0.5 to 1.2. If p+t is 0.5 or more and notmore than 1.2, the crystal structure of the first fluorescent material(I) may be stable, and the emission intensity may be high. p+t ispreferably 0.55 or more, and more preferably 0.60 or more, and alsopreferably 1.1 or less, and more preferably 1.05 or less.

In formula (I), s is a compositional molar ratio of Al. If s is 8.5 ormore and not more than 13, the crystal structure may be stable, and theemission intensity of the first fluorescent material (I) may be highwhen excited by light in the near-ultraviolet to blue region. In formula(I), s is preferably 9 or more, and also preferably 13 or less, morepreferably 12 or less, and still more preferably 11 or less.

The first fluorescent material 71 may be produced by using a flux, suchas a halide, to enhance its reactivity as a material. In this case, whena flux containing alkali metal is used, a small amount of alkali metalmay be detected from the fluorescent material 71. Even in such a case,when, for example, the main components of the fluorescent material 71satisfy formula (I), the fluorescent material 71 is a first fluorescentmaterial (I). When the first fluorescent material 71 contains alkalimetal, the alkali metal content ratio is preferably 1000 ppm or less,and more preferably 990 ppm or less, and also preferably 100 ppm ormore, more preferably 200 ppm or more, and still more preferably 300 ppmor more. In the first fluorescent material 71 containing alkali metal,the compositional molar ratio of the alkali metal in the firstfluorescent material 71 is preferably 0.05 mole or less, and morepreferably 0.04 mole or less. When the first fluorescent material 71contains a halogen element, the compositional molar ratio of the halogenelement in the first fluorescent material 71 is preferably 0.12 mole orless, and more preferably 0.1 mole or less.

Examples of the flux include alkali metal fluorides and alkali metalchlorides. Specifically, sodium fluoride (NaF) or potassium fluoride(KF) is preferable, and NaF is more preferable.

The first fluorescent material 71 absorbs light emitted from thelight-emitting element 10, which has a peak emission wavelength in arange of from 400 nm to 470 nm, and emits light having a peak emissionwavelength in a range of from 515 nm to 525 nm. The first fluorescentmaterial 71 emits light having a half bandwidth of the emission spectrumof preferably 45 nm or less, more preferably 40 nm or less, still morepreferably 35 nm or less, and furthermore preferably 30 nm or less whenexcited by light emitted from a light-emitting element having a peakemission wavelength of, for example, 450 nm. The half bandwidth is, forexample, 20 nm or more.

The first fluorescent material 71 is excited by light from alight-emitting element having a peak emission wavelength in a range offrom 400 nm to 470 nm, and emits light having a narrow half bandwidth ofthe emission spectrum in the green region. A liquid crystal displayincluding the light-emitting device including the first fluorescentmaterial can have a wide color reproduction range.

The first fluorescent material 71 has an average particle diameter of,for example, from 5 μm to 50 μm. The first fluorescent material havingan average particle diameter of 5 μm or more may, for example, absorbmore light and have a higher emission intensity. Also, the firstfluorescent material having an average particle diameter of 50 μm orless may have less variation in color among the light-emitting devicesto be produced. The first fluorescent material has an average particlediameter of preferably 5.5 μm or more, more preferably 6 μm or more, andstill more preferably 7 μm or more, and also preferably 48 μm or less,more preferably 45 μm or less, and still more preferably 30 μm or less.

An average particle diameter of a fluorescent material as used herein isa volume average particle diameter (median diameter) at which the volumecumulative frequency from the small diameter side reaches 50%, which isdetermined by using a laser diffraction particle size analyzer (e.g.,MASTER SIZER 3000 by Marvern Instrument Instrument).

Second Fluorescent Material

The fluorescent member 50 included in the light-emitting device 100contains at least one second fluorescent material 72 in addition to thefirst fluorescent material 71 as a green light-emitting fluorescentmaterial. The second fluorescent material is selected from fluorescentmaterials having a different composition from the first fluorescentmaterial and a peak emission wavelength in a range of from 510 nm to 550nm. The second fluorescent material 72 may include a single fluorescentmaterial alone, or two or more in combination.

The second fluorescent material 72 preferably contains at least onematerial selected from the group consisting of β sialon fluorescentmaterials, silicate fluorescent materials, and sulfide fluorescentmaterials. A light-emitting device including at least one fluorescentmaterial selected from these fluorescent materials as the secondfluorescent material 72 in combination with the first fluorescentmaterial 71 can have a further wider color reproduction range. Thesecond fluorescent material 72 preferably has a peak emission wavelengthof from 520 nm to 545 nm. Further, the second fluorescent material 72preferably has a longer peak emission wavelength than the firstfluorescent material. The difference in peak emission wavelength betweenthe first fluorescent material 71 and the second fluorescent material 72is, for example, 30 nm or less, preferably 25 nm or less, and morepreferably substantially 0 nm. The light-emitting device 100 includingthe second fluorescent material 72 having such a peak emissionwavelength can have more light-emitting components at around 555 nm thatcontribute to improving luminance in an extent not to affect theexpansion of the color reproduction range.

The second fluorescent material 72 preferably contains at least onematerial selected from the group consisting of fluorescent materialshaving a composition represented by any of the formulas (IIa) to (IId)below. The light-emitting device 100 including the second fluorescentmaterial 72 having a specific composition can have a wider colorreproduction range. The formula (IIa) represents a composition of βsialon fluorescent materials, the formulas (IIb) and (IId) representcompositions of silicate fluorescent materials, and the formula (IIc)represents a composition of sulfide fluorescent materials.

Si_(6-z)Al_(z)O_(z)N_(8-z):Eu (provided, however, 0≤z≤4.2, andpreferably 0.02≤z≤0.5)  (IIa)

(Ca,Sr)₈MgSi₄O₁₆(Cr,F,Br)₂:Eu  (IIb)

(Sr,Ca,Ba)Ga₂S₄:Eu  (IIc)

(Ba,Sr,Ca)₂SiO₄:Eu  (IId)

The second fluorescent material 72 absorbs light emitted from thelight-emitting element 10 having a peak emission wavelength in a rangeof from 400 nm to 470 nm, and emits light having a peak emissionwavelength in a range of from 510 nm to 550 nm. The second fluorescentmaterial 72 has a half bandwidth of the emission spectrum of preferably100 nm or less, more preferably 80 nm or less, still more preferably 70nm or less, and furthermore preferably 65 nm or less when excited bylight emitted from the light-emitting element 10 having a peak emissionwavelength of, for example, 450 nm. The half bandwidth is, for example,30 nm or more. The light-emitting device 100 including the secondfluorescent material 72 having such a half bandwidth can have morelight-emitting components at around 555 nm that contribute to improvingluminance in an extent not to affect the expansion of the colorreproduction range.

The ratio of the half bandwidth of the second fluorescent material 72 tothe half bandwidth of the first fluorescent material 71 is, for example,1 or more, preferably 1.1 or more, and, for example, 2.5 or less, andpreferably 1.8 or less. With the ratio of the half bandwidth in therange above, a wider color reproduction range can be obtained. When thedifference in peak emission wavelength between the first fluorescentmaterial 71 and the second fluorescent material 72 is substantially 0nm, and the ratio of the half bandwidth of the second fluorescentmaterial 72 to the half bandwidth of the first fluorescent material 71is 1.1 or more, an even wider color reproduction range may be obtained.

To achieve high emission efficiency, the second fluorescent material 72has an average particle diameter of, for example, 2 μm or more,preferably 5 μm or more, and more preferably 7 μm or more, and also, forexample, 50 μm or less, preferably 45 μm or less, and more preferably 42μm or less.

To achieve a desired color reproducibility, the first fluorescentmaterial 71 and the second fluorescent material 72 content in thefluorescent member 50 is, for example, 50 parts by weight or more,preferably 60 parts by weight or more, and more preferably 70 parts byweight or more, and, for example, 250 parts by weight or less,preferably 220 parts by weight or less, and more preferably 200 parts byweight or less relative to 100 parts by weight of the resin in thefluorescent member 50.

When the second fluorescent material 72 is a β sialon fluorescentmaterial, the content ratio of the second fluorescent material 72relative to the total amount of the first fluorescent material 71 andthe second fluorescent material 72 in the fluorescent member 50 is, forexample, less than 10% by weight, preferably 5% by weight or less, morepreferably 3% by weight or less, and also, for example, 0.05% by weightor more. When the second fluorescent material 72 is a silicatefluorescent material, the content ratio of the second fluorescentmaterial 72 is, for example, less than 1% by weight, preferably 0.5% byweight or less, and more preferably 0.3% by weight or less, and forexample 0.01% by weight or more. When the second fluorescent material 72is a sulfide fluorescent material, the content ratio of the secondfluorescent material 72 is, for example, less than 0.5% by weight,preferably 0.1% by weight or less, and more preferably 0.05% by weightor less, and for example 0.01% by weight or more.

Third Fluorescent Material

The fluorescent member 50 included in the light-emitting device of thepresent embodiment includes the third fluorescent material 73, which hasa peak emission wavelength in a range of from 620 nm to 670 nm. Thethird fluorescent material is selected from fluorescent materials havinga peak emission wavelength in a range of from 620 nm to 670 nm. Thethird fluorescent material 73 may contain a single fluorescent materialalone or two or more in combination.

The third fluorescent material 73 preferably contains at least onematerial selected from the group consisting of fluoride fluorescentmaterials, magnesium fluoro-germanate fluorescent materials, nitridefluorescent materials, and sulfide fluorescent materials. Alight-emitting device including the third fluorescent material 73 thatis at least one selected from these fluorescent materials can have awider color reproduction range.

The third fluorescent material 73 preferably contains at least onematerial selected from the group consisting of fluorescent materialshaving a composition represented by any of the formulas (IIIa) to (IIIe)below. A light-emitting device including a fluorescent material havingsuch a specific composition can have a wider color reproduction range.The formula (IIIa) represents a composition of fluoride fluorescentmaterials, the formula (IIIb) represents a composition of magnesiumfluoro-germanate fluorescent materials, the formulas (IIIc) and (IIId)represent compositions of nitride fluorescent materials, and the formula(IIIe) represents a composition of sulfide fluorescent materials.

K₂(Si,Ge,Ti)F₆:Mn  (IIIa)

3.5MgO.0.5MgF₂.GeO₂:Mn  (IIIb)

(Sr,Ca)AlSiN₃:Eu  (IIIc)

(Sr,Ca)LiAl₃N₄:Eu  (IIId)

(Ca,Sr)S:Eu  (IIIe)

The third fluorescent material 73 absorbs light emitted from thelight-emitting element 10, which has a peak emission wavelength in arange of from 400 nm to 470 nm, and emits light having a peak emissionwavelength in a range of from 620 nm to 670 nm. The third fluorescentmaterial has a half bandwidth of the emission spectrum of preferably 100nm or less, more preferably 80 nm or less, still more preferably 70 nmor less, and furthermore preferably 65 nm or less, when excited by lightfrom the light-emitting element 10 having a peak emission wavelength of,for example, 450 nm. The half bandwidth can be, for example, 3 nm ormore.

To achieve high emission efficiency, the third fluorescent material 73has an average particle diameter of, for example, 2 μm or more,preferably 5 μm or more, and more preferably 7 μm or more, and also, forexample, 50 μm or less, preferably 45 μm or less, and more preferably 42μm or less.

To achieve a desired color reproduction range, the third fluorescentmaterial 73 content in the fluorescent member 50 is, for example, 0.5part by weight or more, preferably 1 part by weight or more, morepreferably 3 parts by weight or more, and also, for example, 100 partsby weight or less, preferably 90 parts by weight or less, and morepreferably 80 parts by weight or less relative to 100 parts by weight ofthe resin in the fluorescent member 50.

The ratio of the green fluorescent material, which includes the firstfluorescent material 71 and the second fluorescent material 72, to thered fluorescent material, which includes the third fluorescent material73, in the fluorescent member 50 (the green fluorescent material:the redfluorescent material) is, for example, from 5:95 to 99:1, preferablyfrom 20:80 to 98:2, more preferably from 30:70 to 97:3, still morepreferably from 40:60 to 96:4, and particularly preferably from 50:50 to95:5. A light-emitting device including the fluorescent member 50containing the green fluorescent material and the red fluorescentmaterial in the range above can have a wider color reproduction range.

Other Fluorescent Materials

The fluorescent member 50 may contain other fluorescent materials inaddition to the first fluorescent material 71, the second fluorescentmaterial 72, and the third fluorescent material 73 as appropriate.Examples of the other fluorescent materials include(Y,Gd,Tb,Lu)₃(Al,Ga)₅O₁₂:Ce, Ca₃Sc₂Si₃O₁₂:Ce, CaSc₂O₄:Ce,(La,Y)₃Si₆N₁₁:Ce, (Ca,Sr,Ba)₃Si₆O₉N₄:Eu, (Ca,Sr,Ba)₃Si₆O₁₂N₂:Eu, and(Ba,Sr,Ca)Si₂O₂N₂:Eu. When the light-emitting device contains otherfluorescent materials, the other fluorescent material content isselected as appropriate in accordance with, for example, the purpose.The other fluorescent material content relative to a total amount of thefirst fluorescent material 71, the second fluorescent material 72, andthe third fluorescent material 73 is, for example, 5% by mass or less,and preferably 2% by mass or less.

The light-emitting device 100 has a relative emission intensity at 500nm of 35% or less, preferably 30% or less, and more preferably 25% orless when the local maximum emission intensity in a range of from 510 nmto 535 nm in the emission spectrum is taken as 100%. The relativeemission intensity at 540 nm is 65% or less, preferably 60% or less, andmore preferably 55% or less. With the relative emission intensity in therange above, each emission of blue, green, and red in the emissionspectrum of the light-emitting device is emphasized in the respectiveblue and red-light wavelength regions and the green light wavelengthregion between them, which has strong influence on the colorreproduction range. This increases color purity of each color, and canexpand the color reproduction range of a liquid crystal displayincluding the light emitting device. When there are two or more localmaximum values of emission in a range of from 510 nm to 535 nm, themaximum emission intensity among them is used as a reference.

To achieve high color reproduction range and high luminance, the peakemission wavelength in the range of from 510 nm to 535 nm in theemission spectrum, or in the green region, is, for example, from 512 nmto 530 nm, and preferably from 514 nm to 528 nm. The half bandwidth is,for example, from 20 nm to 40 nm, and preferably from 23 nm to 35 nm.

The light-emitting device 100 emits mixed light of light from thelight-emitting element and light emitted from the first fluorescentmaterial 71, the second fluorescent material 72, and the thirdfluorescent material 73. The chromaticity values of the mixed light inthe CIE 1931 xy chromaticity coordinates are: for example, x in a rangeof from 0.22 to 0.34 and y in a range of from 0.16 to 0.34, preferably xin a range of from 0.22 to 0.33 and yin a range of from 0.17 to 0.33.

EXAMPLES

Examples of the present disclosure will now be described in detail, butthe present invention is not limited to these Examples.

Fluorescent Material

Before producing the light-emitting devices of examples and comparativeexamples, the first and second fluorescent materials, which emit green,and a third fluorescent material, which emits red, were each prepared.As the first fluorescent material, Fluorescent Materials A and A2, andas the second fluorescent material, Fluorescent Materials B to D shownin Table 1 were prepared.

Fluorescent Material A

As Fluorescent Material A, a fluorescent material having a compositionrepresented by formula (I): X¹_(p)Eu_(t)Mg_(q)Mn_(r)Al_(s)O_(p+t+q+r+1.5s) (wherein X¹ is Ba, and thecompositional molar ratio satisfies t=0, p=1.0, q=0.5, r=0.5, ands=10.0) was prepared. Specifically, BaCO₃, MgO, MnCO₃, Al₂O₃, and MgF₂were prepared as raw materials, and NaF was prepared as a flux. Thesewere weighed so that the molar ratio BaCO₃:MgO:MgF₂:MnCO₃:Al₂O₃:NaFsatisfies 1.0:0.4:0.1:0.5:10.0:0.1, and mixed to obtain a mixture. Themixture was charged into an alumina crucible, and heat-treated at 1500°C. for 5 hours in a mixed gas atmosphere of H₂/N₂=3/97 (volume ratio)under ordinary pressure to obtain powder.

To the resultant powder, light having an excitation wavelength of 450 nmwas applied, and its emission spectrum at room temperature (25° C.±5°C.) was measured using a quantum efficiency measurement system (QE-2000by Otsuka Electronics), and the wavelength at which the emissionintensity was maximum was determined as a peak emission wavelength (nm).The peak emission wavelength of the powder was 517 nm. The powder wasused as Fluorescent Material A having a composition represented byBa_(1.0)Mg_(0.5)Mn_(0.5)Al₁₀O₁₇.

Fluorescent Material A2

As Fluorescent Material A2, a fluorescent material having a compositionrepresented by formula (I): X¹_(p)Eu_(t)Mg_(q)Mn_(r)Al_(s)O_(p+t+q+r+1.5s) (wherein X¹ is Ba, and thecompositional molar ratio satisfies t=0.1, p=0.9, q=0.5, r=0.5, ands=10.0) was prepared. Specifically, BaCO₃, Eu₂O₃, MgO, MnCO₃, Al₂O₃, andMgF₂ were prepared as raw materials, and NaF was prepared as a flux.These were weighed so that the molar ratioBaCO₃:Eu₂O₃:MgO:MgF₂:MnCO₃:Al₂O₃:NaF satisfies0.9:0.1:0.4:0.1:0.5:10.0:0.1, and mixed to obtain a mixture. The mixturewas heat-treated in the same manner as Fluorescent Material A to obtainpowder.

The peak emission wavelength of the powder measured in the same manneras Fluorescent Material A was 517 nm. The powder was used as FluorescentMaterial A2 having a composition represented byBa_(0.9)Eu_(0.1)Mg_(0.5)Mn_(0.5)Al₁₀O₁₇.

Fluorescent Material B

As Fluorescent material B, a fluorescent material having a compositionrepresented by Si_(6-z)Al_(z)O_(z)N_(8-z):Eu (z=0.06) (hereinafter “βsialon fluorescent material”) was prepared. The peak emission wavelengthof Fluorescent Material B, or the β sialon fluorescent material,measured in the same manner as Fluorescent Material A was 529 nm.

Fluorescent Material C

As Fluorescent Material C, a fluorescent material having a compositionrepresented by Ca₈MgSi₄O₁₆Cl₂:Eu (hereinafter also referred to as“chlorosilicate fluorescent material”) was prepared. The peak emissionwavelength of Fluorescent Material C, or the chlorosilicate fluorescentmaterial, measured in the same manner as Fluorescent Material A was 522nm.

Fluorescent Material D

As Fluorescent material D, a fluorescent material having a compositionrepresented by SrGa₂S₄:Eu (hereinafter also referred to as “thiogallate(SGS) fluorescent material”) was prepared. The peak emission wavelengthof Fluorescent Material D, or the SGS fluorescent material, measured inthe same manner as Fluorescent Material A was 535 nm.

Third Fluorescent Material

As the third fluorescent material, which emits red light, a fluorescentmaterial having a composition represented by K₂SiF₆:Mn (hereinafter alsoreferred to as “KSF fluorescent material”) was prepared. The peakemission wavelength of the third fluorescent material, or the KSFfluorescent material, measured in the same manner as FluorescentMaterial A was 631 nm.

For each fluorescent material, the measurements described below werecarried out.

Evaluation of Light Emission Properties

For each of Fluorescent Materials A, A2, B, C, and D, light emissionproperties were measured. The half bandwidth of each emission spectrumwas measured. The results are shown in Table 1. The emission spectra ofthe fluorescent Materials A, B, C, and D normalized with the respectivemaximum emission intensities are shown in FIG. 3. The emission spectrumof Fluorescent Material A2 was approximately the same as FluorescentMaterial A.

TABLE 1 Peak emission Half Fluorescent wavelength bandwidth materialComposition (nm) (nm) A Ba_(1.0)Mg_(0.5)Mn_(0.5)Al₁₀O₁₇ 517 28 A2Ba_(0.9)Eu_(0.1)Mg_(0.5)Mn_(0.5)Al₁₀O₁₇ 517 28 BSi_(6−z)Al_(z)O_(z)N_(8−z): Eu (z = 0.06) 529 50 C Ca₈MgSi₄O₁₆Cl₂: Eu522 63 D SrGa₂S₄: Eu 535 48

Examples 1 to 10, Comparative Examples 1 to 11

The corresponding first fluorescent material, second fluorescentmaterial, the third fluorescent material, and silicone resin were mixedto satisfy each compositional ratio shown in Table 2, and then dispersedand defoamed to have a composition for each fluorescent member. Thecomposition for each fluorescent member was adjusted to have acompositional ratio so that the light-emitting device to be producedemits mixed light having CIE 1931 xy chromaticity coordinates of aroundx=0.26, y=0.22. The composition for each fluorescent member was chargedon a blue light-emitting LED (light-emitting element) having a peakemission wavelength of 455 nm, and then cured to produce eachlight-emitting device 100 as shown in FIG. 1. Fluorescent Material A orA2 as the first fluorescent material, any of Fluorescent materials B toD as the second fluorescent material, and the KSF fluorescent materialas the third fluorescent material were used. In Table 2, the totalamount of the fluorescent materials (% by weight) is a total contentratio (% by weight) of the fluorescent materials in the compositionrelative to the amount of the resin. The details of the fluorescentmaterials show the content ratio of each fluorescent material in thetotal amount of the fluorescent materials (% by weight).

TABLE 2 Total amount of Details of fluorescent materials (wt %) FirstSecond fluorescent First Second Third fluorescent fluorescentmaterial(s) fluorescent fluorescent fluorescent material material (wt %)material material material Comparative Fluorescent — 146.7 93.4 0.0 6.6Example 1 material A Example 1 Fluorescent 139.3 93.1 0.1 6.8 Example 2material B 133.7 92.3 0.5 7.2 Example 3 118.0 91.4 0.9 7.7 Example 4125.3 88.7 4.7 6.6 Comparative 76.4 79.6 8.8 11.5 Example 2 Comparative18.3 0.0 46.8 53.2 Example 3 Example 5 Fluorescent 123.3 92.4 0.1 7.5Example 6 material C 87.1 89.3 0.4 10.3 Comparative 62.0 84.8 0.9 14.3Example 4 Comparative 42.8 73.2 2.3 24.5 Example 5 Comparative 17.7 0.012.4 87.6 Example 6 Example 7 Fluorescent 85.5 89.7 0.1 10.3 Comparativematerial D 59.6 85.0 0.4 14.5 Example 7 Comparative 44.8 79.2 0.8 20.0Example 8 Comparative 13.7 0.0 5.3 94.7 Example 9 ComparativeFluorescent — 138.0 92.8 0.0 7.2 Example 10 material A2 Example 8Fluorescent 138.5 92.7 0.1 7.3 Example 9 material B 120.0 90.6 0.9 8.5Example 10 76.6 83.8 4.4 11.8 Comparative 56.5 75.5 8.4 16.2 Example 11

For each light-emitting device, the following measurements were carriedout. The results are shown in Table 3. Table 3 shows the types of thefirst and second fluorescent materials, and the ratio of the secondfluorescent material (% by weight) to the total amount of the firstfluorescent material and the second fluorescent material.

Color Reproduction Range

Simulations were performed using the emission spectrum data of eachlight-emitting device determined by a total luminous flux measurementsystem including an integrating sphere and the transmittance curve dataof color filters. Assuming the color reproduction range according to BT.2020 of the liquid crystal display including the light-emitting deviceof Comparative Example 1 as 100%, the relative BT. 2020(%) values ofliquid crystal displays each including any of the other light emittingdevices were calculated. Also, the luminous intensity (cd/m²) of eachliquid crystal display was calculated, and assuming the luminousintensity (cd/m²) of the liquid crystal display including thelight-emitting device of Comparative Example 1 as 100%, the relativevalue of the luminance (%) of each liquid crystal display wascalculated. For color filters, color filters having a color reproductionrange according to BT. 2020 of about 80% when used in a liquid crystaldisplay including the light-emitting device of Comparative Example 1were used.

Relative Luminous Flux

The luminous flux of each light-emitting device was measured using atotal luminous flux measurement system with an integrating sphere.Assuming the luminous flux of the light-emitting device of ComparativeExample 1 as 100%, the relative luminous flux of each of the otherlight-emitting devices was calculated.

Chromaticity Coordinates (x,y)

Simulations were performed using the emission spectrum data of eachlight-emitting device and the transmittance curve data of the colorfilters. Chromaticity values (x, y) of light having passed through thefilters were obtained as numerical values (x, y) in the CIE 1931 xychromaticity coordinates.

Emission Spectrum

The emission spectrum of relative intensity versus wavelength for eachlight-emitting device was measured using the same system (the totalluminous flux measurement system) used for measuring a relative luminousflux. Assuming the local maximum emission intensity in a range of from510 nm to 535 nm of the emission spectrum of each light-emitting deviceas 100%, the relative emission intensities at 500 nm and 540 nm to thelocal maximum emission intensity were calculated. For eachlight-emitting device, Table 3 shows the wavelength giving the localmaximum emission intensity as λp Green (nm), the relative emissionintensity at 500 nm as I₅₀₀(%), and the relative emission intensity at540 nm as I₅₄₀(%). Also, FIGS. 4 to 7 show the emission spectrum of eachlight-emitting device. The emission spectrum of each light-emittingdevice was normalized with the local maximum emission intensity in arange of from 510 nm to 535 nm.

TABLE 3 Second Relative First Second fluorescent Relative luminousChromaticity fluorescent fluorescent material ratio BT.2020 Luminanceflux coordinates λp Green I₅₀₀ I₅₄₀ material material (wt %) (%) (%) (%)x y (nm) (%) (%) Comparative Fluorescent — — 100.0 100.0 100.0 0.2610.223 516.5 19.3 33.5 Example 1 material A Example 1 Fluorescent 0.1100.2 102.4 102.2 0.262 0.223 516.5 19.7 34.7 Example 2 material B 0.5100.5 102.3 103.1 0.262 0.223 516.5 19.6 37.2 Example 3 1 100.8 109.1110.9 0.262 0.223 516.5 20.2 41.1 Example 4 5 98.8 120.9 128.7 0.2620.223 517.0 23.9 58.4 Comparative 10 97.4 131.2 142.5 0.262 0.223 523.024.2 69.6 Example 2 Comparative 100 94.8 162.1 182.6 0.262 0.223 526.521.5 84.0 Example 3 Example 5 Fluorescent 0.1 99.6 107.6 109.1 0.2620.223 516.5 23.4 37.0 Example 6 material C 0.5 98.1 124.2 129.1 0.2620.223 516.5 33.5 46.0 Comparative 1 95.6 137.7 145.9 0.261 0.223 516.544.5 54.9 Example 4 Comparative 3 93.4 157.7 170.2 0.263 0.223 516.557.6 65.5 Example 5 Comparative 100 91.2 193.8 212.6 0.262 0.223 519.576.2 80.4 Example 6 Example 7 Fluorescent 0.1 99.0 126.4 134.0 0.2620.223 518.0 22.3 56.7 Comparative material D 0.5 96.8 143.9 157.2 0.2620.223 520.0 24.0 75.4 Example 7 Comparative 1 95.6 156.9 174.4 0.2610.223 526.0 24.5 86.4 Example 8 Comparative 100 93.0 199.7 231.1 0.2620.223 534.0 20.5 96.4 Example 9 Comparative Fluorescent — — 100.0 100.0100.0 0.263 0.223 517.0 19.1 35.2 Example 10 material A2 Example 8Fluorescent 0.1 100.1 100.8 101.2 0.262 0.223 517.0 18.9 36.1 Example 9material B 1 100.6 107.5 109.8 0.264 0.223 517.5 19.4 42.2 Example 10 598.6 123.9 131.1 0.262 0.223 518.5 21.2 59.1 Comparative 10 97.2 134.8145.4 0.262 0.223 523.0 21.9 69.4 Example 11

Examples 1 to 4 and Comparative Examples 1 to 3 each include FluorescentMaterial A as the first fluorescent material. Except for ComparativeExample 1, Fluorescent Material B, or the β sialon fluorescent material,is included as the second fluorescent material. As shown in Table 3 andFIG. 4, the light-emitting devices of Examples 1 to 4 have a λp Green ataround 517 nm, a relative emission intensity at 500 nm of 35% or less,and a relative emission intensity at 540 nm of 65% or less. Thus, theamounts of the blue-green component at around 500 nm and theyellow-green component at around 540 nm are small. For eachlight-emitting device, the color reproduction range according to BT.2020 and the luminance of a liquid crystal display including the devicewith the predetermined color filters were obtained. Regarding the colorreproduction range, the liquid crystal displays each including one ofthe light-emitting devices of Examples are about the same. Regardingluminance, Example 4 is higher than Comparative Example 1 by about 20%.In Comparative Examples 2 and 3, the amount of the component at 500 nmis small, whereas the relative emission intensity at 540 nm is greaterthan 65%. Also, the ratio of the β sialon fluorescent material isgreater than 5% by weight. Although Comparative Examples 2 and 3 aremore luminous than Comparative Example 1, there is a large drop in thevalue of color reproduction range, indicating that their colorreproduction ranges are narrow.

Examples 5 and 6 and Comparative Examples 4 to 6 include FluorescentMaterial A as the first fluorescent material, and Fluorescent MaterialC, i.e., the chlorosilicate fluorescent material, as the secondfluorescent material. As shown in Table 3 and FIG. 5, the light-emittingdevices of Examples 5 and 6 each have a λp Green at around 516.5 nm, arelative emission intensity at 500 nm of 35% or less, and a relativeemission intensity at 540 nm of 65% or less. In contrast, ComparativeExamples 4 to 6 have a relative emission intensity at 500 nm of higherthan 35%, and Comparative Example 6 has a relative emission intensity at540 nm of higher than 65%. The color reproduction ranges of Examples 5and 6 are approximately the same as the color reproduction range ofComparative Example 1, and Example 6 has a luminance higher by 24%.Although Comparative Examples 4 to 6 are luminous, their colorreproduction ranges are narrow.

Example 7 and Comparative Examples 7 to 9 include Fluorescent Material Aas the first fluorescent material, and Fluorescent Material D, i.e., theSGS fluorescent material, as the second fluorescent material. As shownin Table 3 and FIG. 6, the light-emitting device of Example 7 has a λpGreen at about 518 nm, a relative emission intensity at 500 nm of 35% orless, and a relative emission intensity at 540 nm of 65% or less. Incontrast, although Comparative Examples 7 to 9 each have a low relativeemission intensity at 500 nm, Comparative Examples 7 to 9 have a highrelative emission intensity at 540 nm. Example 7 has about the samecolor reproduction range as the color reproduction range of ComparativeExample 1, but has a luminance higher by 26%. Comparative Examples 7 to9 have narrow color reproduction ranges.

Examples 8 to 10 and Comparative Examples 10 and 11 include FluorescentMaterial A2 as the first fluorescent material. Except for ComparativeExample 10, Fluorescent Material B, or the β sialon fluorescentmaterial, is included as the second fluorescent material. As shown inTable 3 and FIG. 7, the light-emitting devices of Examples 8 to 10 havea λp Green at around 518 nm, a relative emission intensity at 500 nm of35% or less, and a relative emission intensity at 540 nm of 60% or less.In contrast, although Comparative Example 11 has a low relative emissionintensity at 500 nm, Comparative Example 11 has a relative emissionintensity at 540 nm of higher than 65%. Examples 8 to 10 have colorreproduction ranges approximately the same as the color reproductionrange of Comparative Example 10, and Example 10 has a luminance higherby 24%. Comparative Example 11 has a narrow color reproduction range.

As described above, using the second fluorescent material in addition tothe first fluorescent material as the green light-emitting fluorescentmaterial, and adjusting the emission spectrum in the green region tohave a predetermined shape enables wide color reproduction range andhigh luminance.

The light-emitting device according to an embodiment of the presentinvention including a light emission diode as an excitation light sourcecan be used in various fields including the fields of display lightsources, backlight light sources, general lighting, and in-vehiclelighting. The light-emitting device according to an embodiment of thepresent invention has an improved color reproducibility, and can besuitably used as a backlight light source for a liquid crystal display,such as a monitor or a smart phone, that is required to reproduce deepand clear colors of RGB.

It is to be understood that although the present invention has beendescribed with regard to preferred embodiments thereof, various otherembodiments and variants may occur to those skilled in the art, whichare within the scope and spirit of the invention, and such otherembodiments and variants are intended to be covered by the followingclaims.

Although the present disclosure has been described with reference toseveral exemplary embodiments, it is to be understood that the wordsthat have been used are words of description and illustration, ratherthan words of limitation. Changes may be made within the purview of theappended claims, as presently stated and as amended, without departingfrom the scope and spirit of the disclosure in its aspects. Although thedisclosure has been described with reference to particular examples,means, and embodiments, the disclosure may be not intended to be limitedto the particulars disclosed; rather the disclosure extends to allfunctionally equivalent structures, methods, and uses such as are withinthe scope of the appended claims.

One or more examples or embodiments of the disclosure may be referred toherein, individually and/or collectively, by the term “disclosure”merely for convenience and without intending to voluntarily limit thescope of this application to any particular disclosure or inventiveconcept. Moreover, although specific examples and embodiments have beenillustrated and described herein, it should be appreciated that anysubsequent arrangement designed to achieve the same or similar purposemay be substituted for the specific examples or embodiments shown. Thisdisclosure may be intended to cover any and all subsequent adaptationsor variations of various examples and embodiments. Combinations of theabove examples and embodiments, and other examples and embodiments notspecifically described herein, will be apparent to those of skill in theart upon reviewing the description.

In addition, in the foregoing Detailed Description, various features maybe grouped together or described in a single embodiment for the purposeof streamlining the disclosure. This disclosure may be not to beinterpreted as reflecting an intention that the claimed embodimentsrequire more features than are expressly recited in each claim. Rather,as the following claims reflect, inventive subject matter may bedirected to less than all of the features of any of the disclosedembodiments. Thus, the following claims are incorporated into theDetailed Description, with each claim standing on its own as definingseparately claimed subject matter.

The above disclosed subject matter shall be considered illustrative, andnot restrictive, and the appended claims are intended to cover all suchmodifications, enhancements, and other embodiments which fall within thetrue spirit and scope of the present disclosure. Thus, to the maximumextent allowed by law, the scope of the present disclosure may bedetermined by the broadest permissible interpretation of the followingclaims and their equivalents, and shall not be restricted or limited bythe foregoing detailed description.

All publications, patent applications, and technical standards mentionedin this specification are herein incorporated by reference to the sameextent as if each individual publication, patent application, ortechnical standard was specifically and individually indicated to beincorporated by reference.

What is claimed is:
 1. A light-emitting device comprising: alight-emitting element having a peak emission wavelength in a range offrom 400 nm to 470 nm; and a fluorescent member including a firstfluorescent material containing an aluminate that contains Mg, Mn, andat least one alkali earth metal selected from the group consisting ofBa, Sr, and Ca, and has a peak emission wavelength in a range of from510 nm to 525 nm, a second fluorescent material having a differentcomposition from the first fluorescent material, and a peak emissionwavelength in a range of from 510 nm to 550 nm, and a third fluorescentmaterial having a peak emission wavelength in a range of from 620 nm to670 nm, wherein the light-emitting device has an emission spectrum witha relative emission intensity at 500 nm of 35% or less and a relativeemission intensity at 540 nm of 65% or less when a local maximumlight-emitting emission intensity in a range of from 510 nm to 535 nm istaken as 100%.
 2. The light-emitting device according to claim 1,wherein the first fluorescent material has a composition represented byformula (I):X¹ _(p)Eu_(t)Mg_(q)Mn_(r)Al_(s)O_(p)+_(t)+_(q)+_(r)+_(1.5s)  (I) whereinX¹ is at least one selected from the group consisting of Ba, Sr, and Ca;and p, q, r, s and t satisfy 0.5≤p≤1, 0≤q≤0.7, 0.2≤r≤0.7, 8.5≤s≤13,0≤t≤0.5, 0.5≤p+t≤1.2, and 0.2≤q+r≤1.
 3. The light-emitting deviceaccording to claim 2, wherein X¹ contains Ba, and p satisfies 0.6≤p≤1 inthe formula (I).
 4. The light-emitting device according to claim 2,wherein r satisfies 0.3≤r≤0.6 in the formula (I).
 5. The light-emittingdevice according to claim 1, wherein the second fluorescent materialcontains at least one material selected from the group consisting of βsialon fluorescent materials, silicate fluorescent materials, andsulfide fluorescent materials.
 6. The light-emitting device according toclaim 1, wherein the second fluorescent material contains at least oneselected from the group consisting of fluorescent materials having acomposition represented by any of formulas (IIa) to (IId) below:Si_(6-z)Al_(z)O_(z)N_(8-z):Eu,0≤z≤4.2  (IIa)(Ca,Sr)₈MgSi₄O₁₆(Cr,F,Br)₂:Eu  (IIb)(Sr,Ca,Ba)Ga₂S₄:Eu  (IIc)(Ba,Sr,Ca)₂SiO₄:Eu  (IId).
 7. The light-emitting device according toclaim 6, wherein the second fluorescent material has a compositionrepresented by the formula (IIa), and has a content ratio of less than10% by weight relative to a total amount of the first fluorescentmaterial and the second fluorescent material contained in thefluorescent member.
 8. The light-emitting device according to claim 6,wherein the second fluorescent material has a composition represented bythe formula (IIb) or (IId), and the second fluorescent material has acontent ratio of less than 1% by weight relative to a total amount ofthe first fluorescent material and the second fluorescent materialcontained in the fluorescent member.
 9. The light-emitting deviceaccording to claim 6, wherein the second fluorescent material has acomposition represented by the formula (IIc), and the second fluorescentmaterial has a content ratio of less than 0.5% by weight relative to atotal amount of the first fluorescent material and the secondfluorescent material contained in the fluorescent member.
 10. Thelight-emitting device according to claim 1, wherein the thirdfluorescent material contains at least one material selected from thegroup consisting of fluoride fluorescent materials, magnesiumfluoro-germanate fluorescent materials, nitride fluorescent materials,and sulfide fluorescent materials.
 11. The light-emitting deviceaccording to claim 1, wherein the third fluorescent material contains atleast one material selected from the group consisting of fluorescentmaterials having a composition represented by any one of formulas (IIIa)to (IIIe) below:K₂(Si,Ge,Ti)F₆:Mn  (IIIa),3.5MgO.0.5MgF₂.GeO₂:Mn  (IIIb)(Sr,Ca)AlSiN₃:Eu  (IIIc)(Sr,Ca)LiAl₃N₄:Eu  (IIId)(Ca,Sr)S:Eu  (IIIe)
 12. The light-emitting device according to claim 1,wherein the second fluorescent material has a longer peak emissionwavelength than the first fluorescent material.
 13. The light-emittingdevice according to claim 1, emitting light in a range of x from 0.22 to0.34 and y from 0.16 to 0.34 in CIE 1931 xy chromaticity coordinates.